The use of organofluorine compounds is widespread in fire foams. Fluorosurfactants increase the extinguishing capacity of the foams, especially on liquid and water-immiscible substances. Typically, fire fighting foams are prepared from aqueous concentrates which are diluted with water and foamed using a mechanical device. Typically, for the foam to remain stable during the extinguishing operation, a thickener, preferably a polysaccharide, is added to the concentrate. The presence of the thickener can cause the concentrate to be so thick that the concentrate is difficult to pump efficiently, and therefore can cause proportioning problems during foam generation and application. It can also cause problems with the stability of the concentrate, since the thickener often is found to separate from the concentrate upon storage, especially at elevated temperatures.
Until recently, aqueous film forming foams that were used for fire fighting invariably contained low molecular weight fluorosurfactants and fluoropolymer surfactants having perfluoroalkyl chains where the perfluoroalkyl group was at least a perfluorooctyl group. For example, it was believed that a surfactant required at least a perfluorooctyl moiety to provide the necessary physicochemical attributes for efficient and persistent foam formation for fire fighting applications. See WO03/049813. However, perfluorooctyl moieties have been shown to be environmentally persistent and to accumulate in the livers of test animals, leading to calls for the phase-out of materials, including foam components, containing a perfluorooctyl group. Recent regulatory efforts such as the United States EPA's PFOA Stewardship Program and EC directives pertaining to telomer-based higher homologue perfluorinated surfactants have sought to discourage use of perfluorooctyl-containing components and, ideally to remove fluorosurfactants from foam concentrates completely.
However, preparation of fluorine-free foam extinguishants which reliably achieve the highest firefighting performance, and that are stable on storage remains problematic.